Barium Azacryptand Sodide, the First Alkalide with an Alkaline Earth Cation, Also Contains a Novel Dimer, (Na2)2-

The first barium sodide, with stoichiometry Ba2+(H5Azacryptand[2.2.2]-)Na-·2MeNH2, was synthesized by the reaction of Ba, Na, and H6Azacryptand[2.2.2] in NH3−MeNH2 solution. It was characterized by X-ray crystallography, 23Na MAS NMR, hydrogen evolution, DSC, optical spectroscopy, and magnetic susceptibility. This is the first sodide in which the sodium anions form (Na2)2- dimers. Previous theoretical predictions were verified by a calculation of the potential energy curve for the dimer in the field of the surrounding charges, whose positions were determined from the crystal structure.